The human eye can suffer a number of maladies causing mild deterioration to complete loss of vision. Removal of the natural lens may involve making an incision in the eye and augmenting or replacing the natural lens with an intraocular lens.
Intraocular lenses (IOLs) generally include an optic zone and two haptics. The optic zone is the part of the lens the patient sees, and is manufactured to be free of blemishes or manufacturing indicators. The haptics are used to hold the lens in a desired position and orientation. In some situations, the lens may have a single curvature or surface. In other situations, the lens may be toric or aspheric to correct a particular malady.
An IOL may have an optic zone with a diameter of about 6 mm, and the haptics may extend out to about 13-13.5 mm. During implantation of the lens into a patient, an incision of about 2.4-3.0 mm may be formed in the eye. The IOL may be folded and compressed to fit in a cannula with a diameter of approximately 2 mm. One method of folding the IOL may involve folding the haptics inside the optic zone, so that after the IOL is positioned in the eye, the optic zone unfolds and the haptics can be extended and attached as desired.
Manufacturing an intraocular lens generally includes machining an optic pin to a specified roughness on both optic and haptic zones of the pin. Both of these zones are manually polished to a surface roughness on the order of 0.260 microns or less. The finished optic pin is used to injection mold a pair of wafers used to form the IOL.
A common paradigm in the manufacturing of intraocular lenses is the forming of a haptic zone having the same surface roughness as the surface roughness of the optic zone. One result of having the surface roughness for a haptic zone being the same as the surface roughness of the optic zone is the possibility for the haptic zone to adhere to the optic zone. The adherence of a haptic to the optic zone may be likened to the adherence exhibited between contact surfaces when two smooth or polished surfaces are in contact. The situation may be worse if the contact surfaces are wet. For example, when two glass panes are in contact, separation may be possible only by sliding one pane relative to the other or applying significant forces to pull them apart.
With respect to haptics, the options for a surgeon to separate a haptic from an optic zone may be more limited. In some situations, a haptic that has adhered to the optic zone may release after a short time without intervention by the surgeon, although the surgeon must wait for the haptic to separate from the optic zone. In some situations, a haptic may be adhered to the optic zone but may be released by the surgeon intervening to separate the haptic from the optic zone, such as by using tools to pull the haptic away from the optic zone. In some situations, a haptic may be adhered to the optic zone such that the surgeon is forced to remove the lens and insert a new lens. In these embodiments, there is the danger that the surgeon may damage the bag or other portion of the eye during the removal process, and there is no guarantee that the replacement lens will not have the same difficulties.